(cba:news) old novae in the (northern) summer

Joe Patterson jop at astro.columbia.edu
Mon Jul 21 10:57:13 EDT 2014


Dear CBAers,

Thanks so much for all your kind remarks concerning that asteroid (8794, 
I think).  A cheap way to get into the sky: no risking of life, and you 
don't have to be a mythological figure or fanatical comet-hunter.  The 
Camp Uraniborg reunion, which generated this, was certainly the high 
point of my year!  (Now that someone else seems to have won the British 
Open.)

It's now 80 years since the discovery of DQ Herculis - the day the music 
started - and 60 years since Merle Walker's sensational discovery of its 
4.6 hr orbital and 71 second spin period.  David Cejudo has recently 
obtained a long string of clear nights on this star, and I see that 
despite small aperture and long-ish integrations (30 s), his data is of 
sufficient quality to define all the relevant properties: orbital wave, 
eclipse shape, precise eclipse timing, presence and precise phase of the 
71 s pulse.  Wow!  I was really surprised how readily the star 
surrendered these numbers to a CBA scope.  Beautifully placed in the 
July night sky, too.  So now's the time to go beyond this and obtain a 
really comprehensive many-longitude and several-week campaign on this 
star.  Try for long time series - BUT atmospheric extinction is a 
factor, so the extinction-worry rules apply:
(1) Include the airmass if you can;
(2) Don't go beyond 2 airmasses (or meridian airmass + 1.0)
(3) Consider using a V or V-ish filter (but I don't recommend this for 
the small scopes, since it will really hurt the measurements of pulse 
phase and eclipse times).

And also a fast-timing pulse rule: choose a cycle time less than half 
the cycle you're trying to resolve (71/2 = 35.5 s).  You can go 
*slightly* longer, but definitely no longer than 50 s.  Around 20 s 
would be really ideal, if you can count enought photons.  You might 
spot-check your computer clock occasionally:

www.time.gov

David's comp star appears to be 000-BCB-330, RA=271.84990, DEC=45.82989.
David, is that correct?  What else is known about this star?

Maybe then we can evaluate the possibility that DQ Her was the original 
inspiration for Superman:

http://www.space.com/21949-superman-origin-star-explosion.html

And Tyson is another Uraniborger, too.

     We're piling up a good record studying nova light curves years to 
decades after maximum light.  Snapshot magnitudes are basically the 
AAVSO business, but I'd be interested too, since it impacts which stars 
to select for time-series study.  For the present season, I'd rate V1974 
Cyg, V1500 Cyg, V1494 Aql, HR Del, and V4743 Sgr as top priority - with 
HR Lyr and V446 Her also probably belonging there, but I don't know much 
about those (yet).  Enrique, could you send in your advice to other 
observers concerning V446 Her (a fascinating star, but a crowded field, 
and you have to decide what to do about the contamination)?

    I'm leaving out V339 Del for the moment, despite my previous mention 
and my interest in the star, because I'm not sure it yet shows any 
periodicity.  Maybe someone knows differently?

    I don't list these stars in any order.  It usually pays to select 
one and stick to it for a couple of weeks - after you're reasonably sure 
that the data look good (some of these targets are pretty faint).

    We're also getting good coverage of this month's dwarf novae, 
especially ASASSN-14cv.  Keep that one up til it disappears (more from 
the USA would be very useful).

Finally, some of our old friends among the DQ Her stars have come back: 
AO Psc, V1223 Sgr, FO Aqr, IGR0023+61.  Especially the first two, for 
whom we're finishing our long-term study this year (and probably this 
summer).

Happy observing!

joe
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